A ferroelectric material is such that once an electric field is applied to cause polarization, the hysteresis characteristics thereof is maintained even if the power supply is cut off. A ferroelectric capacitor, which is formed as a three-layer structure composed of a metal layer, a ferroelectric thin film and a metal layer, is employed as a non-volatile memory by utilizing the polarization characteristics of such a ferroelectric material. Methods of enhancing the performance of a ferroelectric capacitor are increasing the remanent polarization, lowering the operation voltage, lowering the film deposition temperature of the ferroelectric thin film, and improving endurance to repetitive polarization reversal.
In the typical structure of a ferroelectric capacitor, as shown in FIG. 12, a bottom electrode 105, a ferroelectric thin film 106 and a top electrode 107 are formed on a substrate 101 in the order mentioned. A composite oxide film having a perovskite structure such as PZT (PbZrxTi1-xO3), PLZT (Pb1-yLayZrxTi1-xO3) or SBT (SrBi2Ta2O9) is used as the ferroelectric thin film 106. A metal (alloy) comprising one or more metals selected from the group composed of Ru, Rh, Pd, Os, Ir, Pt, Au and Ag, which are highly oxidation resistant under high temperatures, or an electrically conductive oxide comprising one or more oxides selected from the group composed of RuOx, ReOx, RhOx, IrOx and OxOx, is used as the bottom electrode 105 and top electrode 107 of the conventional ferroelectric capacitor. Suppressing degradation of polarization in a case where such metals or conductive oxides is used as the bottom electrode 105 and top electrode 107 is achieved because it is possible to suppress loss of oxygen in the ferroelectric at the ferroelectric—electrode interface.